Kibana version: 5.2.0
Elasticsearch version: 5.2.0
Server OS version: Ubuntu 16.04.2
Browser version: Firefox 50.1.0
Browser OS version: Ubuntu 14.04.5
Original install method (e.g. download page, yum, from source, etc.): Apt
Description of the problem including expected versus actual behavior: Visiting a short URL sometimes produces a 406 error, rather than the expected dashboard.

Steps to reproduce:

1. Share and create shortened URL for Kibana dashboard
2. Visit shortened URL
3. Occasionally a shortened URL is created which produces this error:
   {"statusCode":406,"error":"Not Acceptable","message":"Short url target path must be in the format \"/app/{{appId}}\", found \"/\""}

I have only seen this error twice and am unable to reproduce it for this issue. However I did notice that although the error persists over time (days), as soon as a second short URL is created for the same dashboard, the error no longer occurs.

First occurred immediately after upgrading from 5.1.0 to 5.2.0 .